fix(storage): s3 based images not using browser cache

[thezak48]

This pull request adds an in-memory caching layer for S3 presigned URLs in storage.py to improve performance and reduce unnecessary S3 calls. The cache is thread-safe, supports eviction on asset changes, and ensures URLs are refreshed before expiration. The main changes are grouped below:

Presigned URL Caching:

• Introduced a thread-safe in-memory cache (_presigned_url_cache) for S3 presigned URLs, including logic to store, retrieve, and evict cached URLs with expiration handling. [1] [2] [3]
• Updated get_presigned_image_url to use the cache, returning a cached URL if available and valid, and caching new URLs after generation.

Cache Invalidation:

• Added cache eviction logic in save_upload_file and delete_comparison_assets to ensure the cache remains consistent when assets are added or deleted. [1] [2]

[Copilot]

Pull request overview

This PR adds a per-process, thread-safe in-memory cache for S3 presigned image URLs in storage.py, aiming to reduce repeated S3 calls and keep redirect URLs stable within their TTL.

Changes:

• Added a global presigned-URL cache with locking and expiry handling.
• Updated get_presigned_image_url() to return cached URLs when still valid and cache newly generated URLs.
• Evicted cached entries when uploads overwrite assets or when comparison assets are deleted.

[sonarqubecloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud